From 30af51ce7f4aebb37359367c65b7405451e70702 Mon Sep 17 00:00:00 2001 From: Jeff Cody Date: Mon, 8 Dec 2014 01:07:44 -0500 Subject: [PATCH] block: vhdx - change .vhdx_create default block state to ZERO The VHDX spec specifies that the default new block state is PAYLOAD_BLOCK_NOT_PRESENT for a dynamic VHDX image, and PAYLOAD_BLOCK_FULLY_PRESENT for a fixed VHDX image. However, in order to create space-efficient VHDX images with qemu-img convert, it is desirable to be able to set has_zero_init to true for VHDX. There is currently an option when creating VHDX images, to use block state ZERO for new blocks. However, this currently defaults to 'off'. In order to be able to eventually set has_zero_init to true for VHDX, this needs to default to 'on'. This patch changes the default to 'on', and provides some help information to warn against setting it to 'off' when using qemu-img convert. [Max Reitz pointed out that a full stop was missing at the end of the VHDX_BLOCK_OPT_ZERO option help text. I have added it. --Stefan] Signed-off-by: Jeff Cody Reviewed-by: Max Reitz Message-id: 85164899eacc86e150c3ceba793cf93b398dedd7.1418018421.git.jcody@redhat.com Signed-off-by: Stefan Hajnoczi --- block/vhdx.c | 6 ++++-- qemu-doc.texi | 6 +++++- 2 files changed, 9 insertions(+), 3 deletions(-) diff --git a/block/vhdx.c b/block/vhdx.c index bec10bd09c..46d504c96c 100644 --- a/block/vhdx.c +++ b/block/vhdx.c @@ -1774,7 +1774,7 @@ static int vhdx_create(const char *filename, QemuOpts *opts, Error **errp) log_size = qemu_opt_get_size_del(opts, VHDX_BLOCK_OPT_LOG_SIZE, 0); block_size = qemu_opt_get_size_del(opts, VHDX_BLOCK_OPT_BLOCK_SIZE, 0); type = qemu_opt_get_del(opts, BLOCK_OPT_SUBFMT); - use_zero_blocks = qemu_opt_get_bool_del(opts, VHDX_BLOCK_OPT_ZERO, false); + use_zero_blocks = qemu_opt_get_bool_del(opts, VHDX_BLOCK_OPT_ZERO, true); if (image_size > VHDX_MAX_IMAGE_SIZE) { error_setg_errno(errp, EINVAL, "Image size too large; max of 64TB"); @@ -1936,7 +1936,9 @@ static QemuOptsList vhdx_create_opts = { { .name = VHDX_BLOCK_OPT_ZERO, .type = QEMU_OPT_BOOL, - .help = "Force use of payload blocks of type 'ZERO'. Non-standard." + .help = "Force use of payload blocks of type 'ZERO'. "\ + "Non-standard, but default. Do not set to 'off' when "\ + "using 'qemu-img convert' with subformat=dynamic." }, { NULL } } diff --git a/qemu-doc.texi b/qemu-doc.texi index ad418f851d..aabe8df2f3 100644 --- a/qemu-doc.texi +++ b/qemu-doc.texi @@ -698,7 +698,11 @@ Supported options: Specifies which VHDX subformat to use. Valid options are @code{dynamic} (default) and @code{fixed}. @item block_state_zero -Force use of payload blocks of type 'ZERO'. +Force use of payload blocks of type 'ZERO'. Can be set to @code{on} (default) +or @code{off}. When set to @code{off}, new blocks will be created as +@code{PAYLOAD_BLOCK_NOT_PRESENT}, which means parsers are free to return +arbitrary data for those blocks. Do not set to @code{off} when using +@code{qemu-img convert} with @code{subformat=dynamic}. @item block_size Block size; min 1 MB, max 256 MB. 0 means auto-calculate based on image size. @item log_size -- 2.39.2